Organic bonded abrasive product



Patented Nov. 14, l95

UNITED STATES PATENT OFFICE ORGANIC BONDED ABRASIVE PRODUCT No Drawing. Application July 8, 1948, Serial No. 37,513. In Great Britain September 30, 1947 7 Claims.

The invention relates to grinding wheels and other abrasive products such as segments and it contemplates an improved organic bond for theabrasive grains giving improved results in particular applications.

One object of the invention is to make a superior steel centered coping wheel. Another object of the invention is to make superior organic bonded segments. Another object of the invention is to provide an improved composition for' grinding all kinds of stone such as granite, marble, etc. Another object of the invention is to provide an improved wheel for cutting fire clay.

Another object of the invention is to provide a stronger coping wheel. Another object of the invention is to provide a grinding wheel for use on stone and the like which grinds relatively silently. Another object of the invention is to achieve a better finish when cutting stone. Another object of the invention is to achieve a higher cutting rate when cutting stone. Another object of the invention is to reduce wheel wear when cutting stone.

Another object of the invention is to provide an improved method for the manufacture of essentially shellac bonded abrasive products. Another object of the invention is to so modify shellac bond that abrasive products therewith can be cold molded. Another object of the invention is to provide additional ingredients and steps in the method of mixing whereby essentially shellac bonded abrasive products can be made by cold molding technique thus greatly reducing the cost of manufacture.

Another object of the invention is to provide.

a coping wheel that will not crack. Another object of the invention is to provide a cuttingofl wheel which polishes the edge of the cut. Another object of the invention is to provide coping wheels with wider (radially) rims of abrasive than heretofore considered good practice, which coping wheels will neither crack nor spall. Another object of the invention is to provide a coping wheel which cuts adequately with reduced power consumption.

Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

I provide a quantity of suitable abrasive. This may be any usual or desired abrasive material particularly fused alumina, corundum and silicon carbide, the composition and grit size of the abrasive being chosen according to the nature of the material to be ground and the specific grinding conditions all in accordance with known technology. Selection of relative amounts of abrasive bond and pores varies according to the purposes and conditions for which the Wheel is to be used and may be the same, wheel for wheel, as in the case of normal shellac bonded abrasive products or in some cases may be one structure hum ber higher. That is to say, greatly improved results can be achieved making this new product in the same grade and structure as normal shellac bonded wheels but the very best results are in some cases achieved by making the new product of this invention one structure number higher than the normal shellac bonded product.

The bond is at least 50% by volume shellac. The major part of the remainder of the bond by volume is selected from the group consisting of phenol-formaldehyde and. glyptal. By phenolformaldehyde I means the broad class of phenolic resins in which the phenol constituent may include some cresol or the like. By glyptal I intend the broad class of resins derived from polyb-asic (polycarboxylic) acids and polyhydric alcohols and not merely the condensate of glycerine and phthalic anhydride. The word glyptal is a common name designating this broad class of resins. Furthermore since the glyptals are compatible with the phenolic resins, I definitely intend to include mixtures thereof.

One of the important features of this invention is the use of a plasticizer for the shellac and synthetic resin selected from the group consisting of phenol-formaldehyde, glyptal and mixtures thereof. As such plasticizer I may use nitro parafiin having from two to four' carbon atoms. By nitro parafiin I intend to include the hydroxylated nitro parafiins and the halogenated nitro parafiins and the both hydroxylated and halogenated nitro parafiins because all are usable in the invention. A considerable number of compounds is thereby included but they are all related and have similar properties.

The hydroxylated nitro paraffins are particularly useful in this invention since they have two active groups and I believe that they link together the shellac and phenol-formaldehyde or glyptal to a certain extent. Thus the plasticizer I now prefer is two-nitro butanol which may be written thus: CH3 CH2 CH(NO2) -CH2OH.

Another nitro parafiln which I-have found to be useful in this invention is one-nitro propane which may be written thus: CHa-CH2'CH2(NO2).

I may also use two nitro propane which may be written thus: CH: CH N02) CH3.

I may also use nitro ethane which may be written thus: CH3'CH2(NO2).

All of the foregoing nitro parafiins are now readily available on the market. any of these may be readily halogenated. For example if I want the chlorinated derivative of any of the foregoing compounds it will suflice to bubble chlorine through it in the presence of a suitable catalyst such as phosphorous pentachloride. Chlorine will replace hydrogen on the nitrated carbon first of all, then on the hydroxylated carbon (if any), finally indiscriminately on the other carbon atoms. I may also brominate or iodate these paraflins similarly, that is to say by merely adding bromine or iodine and also a suitable catalyst such as phosphorous pentachloride. The same rules as to replacement apply. As is known for fluorinating it is best to generate the fluorine and pass the paraffin through it in vapor form.

In any case I may start with th appropriate alcohol such as ethyl alcohol, propyl alcohol, isopropyl alcohol, normal primary butanol, normal secondary butanol, primary isobutyl alcohol and tertiary butyl alcohol or mixtures thereof, then halogenate it or not as desired, then nitrate it. Nitrating is done by vaporizing the alcohol or halogenated alcohol and passing it with nitrogen dioxide through a hot zone (about 600 0.). This nitrates the compounds at random but the resultant products are all useful.

Or, a better commercial way is to start with the desired parafiin or mixture of parafiins, then nitrate it by passing it through a hot zone with nitrogen dioxide, then halogenate it in the manner above described, then hydroxylate it by treating it with an alkali (e. g. NaOH) thus leaving a double bond where the halogen was removed, then adding water with a little sulphuric acid which hydroxylates the compound at the double bond. If only one halogen atom was on the molecule this procedure will produce a nitrated alcohol without any halogen, but if more than one halogen atom was on the molecule, the end product will still be halogenated. Of course if the desired product is a nitrated but not hydroxylated or halogenated parafiln, the above process is stopped after nitrating, and if the desired product is a halogenated but not hydroxylated nitro parafiin, the process is stopped after halogenating. As is known to chemists more or less halogen can be put into the molecule by varying the time factor in the halogenating process.

In the case of the fluorinated compounds it is best to start with a fiuorinated Daraifin. These may be made by passing the paraflin hydrocarbon through a fluorine generator. Then the fluorinated parafiin is nitrated by the procedure above described and if desired it may be hydroxylated as above described.

As I have already indicated, the hydroxylated nitro parafllns are preferred and this is true whether or not they contain some halogen. That is to say I prefer nitrated alcohols having from two to four carbon atoms, the alcohols being those indicated and which alcohols may or may not contain halogen. However the nitrated paraflins which are not alcohols with or without halogen are useful in the present invention.

I do not know that the halogenated compounds Furthermore are more useful in the present invention than the unhalogenated compounds but since I do know that they are substantially as useful as the unhalogenated compounds, I wish to include them within the scope of the present invention. Furthermore, as above indicated, the convenient way to make a nitrated alcohol is to halogenate nitrated paraffin, and since the subsequent hydroxylating may not remove all of the halogen (which does no harm anyway), the halogenated compounds clearly fall within th present invention.

The parafllns that are selected for making the compounds useful in the present invention are those from which the above list of alcohols are derived, that is to say ethane, propane, normal butane, and isobutane,

As an example of carrying the invention into practice I take a suitable quantity of abrasive grain and add thereto a mixture of liquid phenolic resin and nitro paraffin.

The quantity of nitro paraffin should be between 5% and 50% inclusive by weight of the liquid phenolic resin. The abrasive grain is first placed in a suitable mixing machine and then the liquid phenolic resin mixed with nitro parafiin is slowly added while continuing the mixing. After a few minutes all of the grain is wetted with the resin-nitro paraifin mixture which is well distributed.

At this point powdered shellac is added to the mixture and the mixing is continued. A suitable filler such as cryolite may likewise be added at this stage but this is optional. The shellac is added slowly and when all of it has been added. the mixing is continued until all of the powder has been picked up by the nitro paraifin on the abrasive grain. This will only take a few minutes at most. As above stated at least 50% by volume of the bond should be shellac, the upper limit of the shellac is by volume. These figures are based on the assumption that the bond is the shellac and the phenolic resin excluding the nitro paraffin and the filler, if any.

If the resultant mixture after a few minutes is dusty, that is to say if there is an appreciable amount of powder which has not been picked up by the liquid nitro paraffin, a dust settling agent should be added and the mixing continued for a short time further. China-wood oil and tung oil are good agents for this purpose. Any amount of either of these two agents can be added up to not more than 10% by weight of the shellac. In many cases especially when the total formula calls for a large percentage of abrasive, it will not be necessary to add any China-wood oil or tung oil or equivalent agent.

A suitable mixture according to the invention having thus been made, a quantity thereof is placed in a mold and pressed cold at a pressure which need not exceed 2000 pounds to the square inch. After pressing, the uncured body is removed from the mold and given a suitable heat treatment which may be curing in an oven for twenty-four hours at C.

As further examples of the invention. liquid glyptal resin may be substituted for the phenolic resin or a mixture of liquid phenolic resin and liquid glyptal resin in any proportions may be substituted. The rest of the procedure can be as above described.

By using one of the above described plasticizers for shellac which is also readily miscible with liquid phenolic resin and liquid glyptal, I am enabledto cold-press various kinds, sizes and shapes of shellac bonded grinding wheels, thereafter anaemia curing them in an oven, and the method and composition achieve actually superior products as well as solving a difficult manufacturing problem. One of the outstanding uses for shellac bonded grinding wheels has long been for the grindin of razor blades. Such wheels have been long cylinders and heretofore have been made by hot molding technique. That is to say, cold shellac cannot be compacted by pressing so therefore such long cylinders had to be made by simultaneously heating and pressing the contents of the mold. In the case of such large wheels this operation took considerable time and thus to make one wheel required the use of expensive equipment for a long time. According to the present invention I can make such wheels by a quick cold pressing operation followed brewing in an oven which simultaneously cures not one but scores of wheels of divers kinds and sizes.

When embodied in coping wheels, the present invention provides wheels which are superior to the best prior art product. Using the usual traverse type of stone saw, cutting wet an assortment of stone from hard to soft, coping wheels according to the invention showed a marked increase in production and life of the wheel over the best prior art coping wheels. Cutting white Italian marble with wheels of the invention, the number of superficial feet cut was 50% higher than with standard coping wheels. When cutting hard York silica stone using wheels according to the invention, the increase in superficial feet out per wheel (as compared with the best prior art wheels) was up to 150% while the speed of cut was twice that of the prior art wheels.

Although the use of water as a lubricant promotes longer wheel life, its main object is to prevent the burning of materials which discolor rapidly when subjected to high temperatures. All stone. and slate especially, has a strong tendency to burn or spall when cutting is attempted with wheels too hard or at an excessive speed even with a copious supply of water, so it is particularly significant that when using wheels according to this invention an operator was unable to burn hard dense slate even when forcingthe rate of feed to such an extent as to stall the motor, while white Italian marble three inches in depth was cut right through without the aid of lubricant and without fluxing either the marble or the wheel bond, and the quality of the finished cut was of such excellence that subsequent polishing operations were unnecessary. With a wheel according to the invention the operator was able to cut one of the hardest of known granites, i. e. RedSwede. A through cut of one inch depth was accomplished with only a five horse power motor and the time taken was only four times longer than that of a diamond wheel, and here again the finish was so good that only a slight polishing was necessary, eliminating flve subsequent operations. It may be observed that any wheel which is as good as one quarter that of a diamond wheel is'quite competitive with diamond wheels because of the great cost thereof.

Coping wheels made according to the invention are definitely stronger than previous types. One manufacturer decided to stop manufacturing coping wheels with more than one inch of usable abrasive owing to incessant complaints of wheels breaking. However coping wheels according to the invention were made with two inches of usable abrasive. These were used mainly for cutting seven foot lengths of three inch thick hard York stone. This is a hazardous operation for any type of wheel; these wheels according to the invention stood up to this test successfully. Atone plant coping wheels according to the inventionhaving two inches of usable abrasive have worn to a knife edge and still have not broken away from the steel center. These wheels were used for cutting 47% alumina fire bricks and 7300 cuts 10" x 4" were made (over twice normal production) with each wheel. Another feature of wheels according to the invention is their great flexibility (comparatively) and remarkable resistance to stresses. It has been found that wheels according to the invention grind relatively silently which of course relieves strain on the workers.

Still another advantage of the present invention is that old or used steel centers can be employed for the manufacture of new wheels. While in some cases this has been done heretofore there have been difficulties and some plants have refused to use the old centers for the manufacture of new coping wheels. A mixture according to the present invention is so highly plastic and workable that no difliculty is experienced making new wheels with old steel centers.

It will thus be seen that there has been provided by this invention an abrasive product and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments might be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all. without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. An abrasive article comprising abrasive grains bonded with a bond comprising from 50 volume percent to volume percent of shellac, at least 50 percent of the remainder of the bond by volume being synthetic resin selected from the group consisting .of phenol formaldehyde and glyptal and mixtures thereof, and said bond containing between 5 percent and 50 percent inclusive of nitroparailin having between 2 and 4 carbon atoms by weight based on the synthetic 'resin.

2. An abrasive article according to claim 1 in which the nitro paraffin is hydroxylated.

3. An abrasive article according to claim 2 in which the nitro paraflin is 2-nitro butanol.

4. An abrasive article according to claim 1 in which the nitro paraffin is a nitro propane.

5. An abrasive article according to claim 1 in which the nitro paraffin is nitro ethane.

6. Method of making an abrasive article comprising preparing a mixture of nitro paramn having between 2 and 4 carbon atoms and liquid resin selected from the group consisting of phenol formaldehyde and glyptal and mixtures thereof, wetting a quantity of abrasive grains with said mixture of nitro paraflin and resin, then adding shellac in powdered form and continuing the mixing, cold pressing into an abrasive shape a quantity of the resultant mixture, then curing the cold pressed shape in an oven.

7. Method of making an abrasive article according to claim 6 in which the cold pressing is done with a pressure which does not exceed 2000 pounds to the square inch.

ERNEST DOUGLAS TEAGUE.

(References on following page) 7 REFERENCES CITED IORIIGN PATENTB The following references are of record in the Number Country Date file of this went: 323.449 Greet Brltlin Dec. 3, 1929 UNITED STATES PATENTS 5 OTHER REFERENCES Number Name Date "The Nitroparamns," Commercial Solvent 1,965,016 Webster July 3, 1934 Corp me 10. 

1. AN ABRASIVE ARTICLE COMPRISING ABRASIVE GRAINS BONDED WITH A BOND COMPRISING FROM 50 VOLUME PERCENT TO 95 VOLUME PERCENT OF SHELLAC, AT LEAST 50 PERCENT OF THE REMAINDER OF THE BOND BY VOLUME BEING SYNTHETIC RESIN SELECTED FROM THE GROUP CONSISTING OF PHENOL FORMALDEHYDE AND GLYPTAL AND MIXTURES THEREOF, AND SAID BOND CONTAINING BETWEEN 5 PERCENT AND 50 PERCENT INCLUSIVE OF NITROPARAFFIN HAVING BETGWEEN 2 AND 4 CARBON ATOMS BY WEIGHT BASED ON THE SYNTHETIC RESIN. 